It is now common practice to incorporate different types of structural bracing systems into the design and construction of multiple story buildings in regions that are at risk for occurrences of earthquakes. Such bracing systems are generally integrated into the foundations of building and their upward-extending structural support infrastructure to reduce seismically induced damages that may occur during earthquake events. The most commonly used approaches include bracing systems that: (i) isolate the foundation from its upward-extending support infrastructure so that seismic energy received by the foundation is not fully transmitted to the support infrastructure, (ii) ductile structural bracing systems designed to deform under forces generated by seismic energy received by the foundation, and (iii) ductile self-centering bracing systems configured to resist seismic forces by tensile and compressive deformation.
Base-isolation systems typically use structural elements with very low stiffness to isolate the support infrastructure from its foundation. However, base-isolation systems are difficult and expensive to repair after damage from severe seismic events.
Ductile beam-column connection systems are currently the most widely practised method for designing structures against earthquake loads. However, a problem with such structural systems is that such designs allow nonlinear/plastic deformations in the beam plastic hinge region. Once permanent deformation occurs as a consequence of a seismic event, the damaged supporting components of building infrastructure and its foundation are difficult to repair and often, must be rebuilt or demolished and replaced.
A variety of bracing systems have been proposed for incorporation into building design and construction. Some examples of bracing system include (i) buckling restrained braces such as those disclosed in U.S. Pat. Nos. 6,826,874, 8,424,252, and US Patent Application Publication No. 2013/0205690, (ii) a cast structural fuse device for bracing members that flex under dynamic tension and compression such as disclosed in U.S. Pat. No. 8,683,758, (iii) self-centering energy dissipation devices such as disclosed in US Patent Application Publication No. 2012/0266548, (iv) use of novel memory alloys in self-centering seismic isolation devices (Dolce et al. 2000, Implementation and testing of passive control devices based on shape memory alloys. Earthquake Eng. Struct. Dyn. 29(7), 945-968; Dolce et al., 2001, SMA Re-centering Devices for Seismic Isolation of Civil Structures. Proc. SPIE 4330, 238-249), and (v) reusable hysteretic damping brace disclosed by Zhu et al. (2007, Seismic behaviour of self-centring braced frame buildings with reusable hysteretic damping brace. Earthquake Engineering & Structural Dynamics. 36:1329-1346). Buckling restrained braces and flexing fuse devices resist seismic forces by deforming into nonlinear ranges. They exhibit fat hysteresis loops which contribute to higher amount of damping and thus can reduce velocity and acceleration of the system. However, the problem with buckling restrained braces and flexing fuse devices is the neither type is capable of self-centering after the application of seismic energy ceases. The problem with the above-noted self-centering dissipation devices is that the methods required for their construction are costly and therefore, they have not been widely adopted by the construction industry.